The present patent application claims priority from Japanese patent applications Nos. 2000-306632 filed on Oct. 2, 2000, 2000-306638 filed on Oct. 2, 2000, 2000-327013 filed on Oct. 20, 2000, 2001-266045 filed on Sep. 3, 2001, 2001-266046 filed on Sep. 3, 2001, 2001-299469 filed on Sep. 28, 2001, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an ink jet recording apparatus that ejects ink droplets from a recording head toward a recording medium that is being fed by paper-feeding rollers and following rollers while being held between the rollers.
Further, the present invention relates to an ink jet recording apparatus, in particular, to an inkjet printer capable of performing both unidirectional printing and bidirectional printing.
2. Description of the Related Art
An ink jet printer, that is one of an ink jet recording apparatus, generally supplies a recording medium such as paper via an auto-sheet feeder (automatic successive sheet-feeding mechanism) or manually via a paper feed-in openings, and then feed the recording medium into a gap between a paper-feeding roller and a following roller. While the paper is transported by rotating the paper-feeding roller, a pressure is applied to ink in a pressure-generating chamber of a recording (printing) head so as to eject ink droplets toward the paper, thereby information is printed onto the paper.
The above ink jet printer can normally perform printing on both plain paper and thick paper. In order to keep a printing quality high and substantially constant, a distance defined between a paper surface and a plane on which nozzle openings are arranged, i.e., a paper gap, is required to be always kept approximately constant by moving and adjusting the print head by means of a moving means for the print head.
The plain paper has a thickness of about 0.6 mm or less, containing the variation, for example. In this case, the print head is controlled to move to adjust the paper gap to realize about 1.2 mm. On the other hand, the thick paper has a thickness of about 0.7 mm to 1.5 mm containing the thickness variation. Thus, a position of the print head for the thick paper is moved upward from the position for the plain paper by about 0.9 mm.
Moreover, a serial non-impact type ink jet printer, for example, can select either unidirectional printing or bidirectional printing in a case of printing black-and-white text data such as characters, numerical characters and pieces of ruled lines. In the unidirectional printing, printing is performed in a predetermined one of two directions contained in a main scanning direction (i.e., a horizontal direction). This printing may be called as a high-quality printing mode. On the other hand, in the bidirectional printing, printing is performed both in a direction from left to right and a direction from right to left that correspond to the two directions contained in the main scanning direction. Such a printing may be called as a high-speed printing mode.
In the unidirectional printing, the printing is always performed in a predetermined direction. Thus, a path of the printing, that is, the moving amount of the print head, increases, thereby increasing a time required for the printing. In the unidirectional printing, however, effects of shift of printing positions caused by a mechanical accuracy of the print head or the like are extremely small. Therefore, high-quality printing can be achieved. On the other hand, in the bidirectional printing, the printing is performed from both ends in the horizontal direction. Thus, the printing path is reduced to a half of that of the unidirectional printing, thereby shortening the printing time. The bidirectional printing, however, is largely influenced by the printing position shifts. Therefore, in a case of printing what is composed of printing dots connected in a vertical direction (sub-scanning direction), such as a character of a double height size and a ruled line running in the vertical direction, discontinuity of the printing dots may be visualized, thereby degrading the printing quality. Thus, the user can select one of the unidirectional printing and the bidirectional printing for each printing job, i.e., each document, considering a type of the document to be printed.
In addition, the document to be printed may include a part of full-size characters and the like for which the bidirectional printing can be performed, and another part of the double-height-size characters, the vertical ruled lines and the like, which is to be printed by the unidirectional printing. Thus, in the case of selecting one of the unidirectional printing and the bidirectional printing for each printing job, the increase of the unnecessary printing path increases the printing time, or the printing quality is degraded in some parts of the document. Therefore, printing manners have been proposed in which expanded image data is analyzed in order to determine, depending on the contents of the image data, which one of the unidirectional printing and the bidirectional printing is to be performed (Post-examined Japanese Patent Publication No. 4-9153 and Unexamined Japanese Patent Applications (OPI) Nos. 2-233275 and 8-11353, for example)
Moreover, an information recordable disk in which information can be personally recorded, such as a CD-R, CD-RW, DVD-RAM or the like, has been becoming popular in recent years. Also, demands for personally printing a label on the printed disk have been increased. In this case, the label on the information recordable disk can be printed by supplying the information recordable disk with a tray made of extra-thick paper to the ink jet printer. Further, the performances of the ink jet printers have been enhanced in recent years, so that some ink jet printers can perform a high accuracy full-color printing not only on plain paper and special-purpose paper but also on various types of thick paper.
The conventional ink jet printer is designed, based on the assumption that the maximum thickness of paper handled by the ink jet printer is that of the thick paper, in such a manner that the thick paper manually fed in is allowed to press up against the following roller by its leading end and to be sandwiched between the paper-feeding roller and the following roller even if the following roller is pressed against the paper-feeding roller.
The extra-thick paper used for the tray for fixing the information recordable disk, however, has the thickness of about 1.6 mm to 2.5 mm. Thus, if the extra-thick paper is manually fed in and presses up against the following roller by its leading end, the pressing force F at the end of the extra-thick paper PPP works in a direction to rotate the following roller 1, as shown in FIG. 21, failing to push up the following roller 1. Therefore, it is difficult to clamp the extra-thick paper PPP between the paper-feeding roller 2 and the following roller 1.
The above problems can be solved by providing a release member for the following roller in the ink jet printer, which urges the following roller against the paper-feeding roller after the following roller has been released from the paper-feeding roller and then the extra-thick paper has been manually inserted into a space between the paper-feeding roller and the following roller. In a conventional ink jet printer having such a release member, however, an operation lever for the moving means for the print head and an operation lever for the release member for the following roller are provided separately from each other. Thus, the mechanism becomes complicated and cannot be determined uniquely, and therefore the design of the mechanism also becomes complicated and the design error tends to occur.
Moreover, the thick paper has the thickness of about 0.7 mm to 1.5 mm, as described above. This means the thickness of the thick paper has variation of about 0.8 mm. Moreover, in a case of extra-thick paper for printing CD-R or the like, the thickness is in the range of about 1.6 mm to 2.5 mm. Thus, the variation range of the thickness reaches about 0.9 mm. As described above, the thickness of the thick paper or the extra-thick paper changes depending on the type of paper, thus causing large differences of the paper gap between the types of paper.
Therefore, when relatively thin thick-paper is used, the paper gap becomes large and the shifts of dot-printing positions between the two directions in the bidirectional printing also become large. This may cause the printing quality to be degraded. There are some printers that can correct the positional shifts with a constant rate in the bidirectional printing. Such correction, however, is performed based on the assumption that the paper gap is constant. Thus, when the paper thickness changes depending on the type of the thick paper, stable printing quality cannot be achieved. Moreover, if a correction value in the above correction is changed to be several values depending on the type of the thick paper, causing control of the printing to be extremely complicated.
Therefore, it is an object of the present invention to provide an ink jet recording apparatus, which is capable of overcoming the above drawbacks accompanying the conventional art. More specifically, it is an object of the present invention to provide an ink jet recording apparatus that can uniquely adjust a recording head and a following roller simply. Further, it is another object of the present invention to provide an ink jet recording apparatus that can perform high accuracy printing with stable printing quality on any type or thickness of thick paper. The above and other objects can be achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention.
According to the first aspect of the present invention, an ink jet recording apparatus having a feed roller and a following roller operable to interpose recording medium and to feed the recording medium, and a recording head operable to eject ink droplets onto the recording medium, the apparatus comprises: a paper gap switching portion operable to switch paper gaps by moving the recording head; a pressing-force adjustment portion operable to apply a pressure to the following roller or release the pressure to adjust a pressing force applied to the recording medium; and an operation member operable to operate in series two series of driving operations including a driving operation of the paper gap switching portion and a driving operation of the pressing-force adjustment portion.
Thus, since the paper gap switching portion and the pressing-force adjustment portion can be operated by the operation of the operation member only, it is possible to smoothly perform the switching of the paper gaps and the adjustment of the pressing force without fail, improving the user""s operability. Moreover, since the functions of switching the paper gaps and adjusting the pressing force are integrated with the function of operating those functions, the structures of the operation member, the paper gap switching portion and the pressing-force adjustment portion can be made simple, so that the design can be simplified and, therefore, the design error can be reduced. In addition, the cost for the manufacture and assembly and the number of the processes of the manufacture and assembly can be reduced.
The operation member may include an intermittent gear operable to switch and transmit the two series of driving operations. Thus, the switching of the two series of driving operations can be mechanically realized by simple components and therefore the switching operations can be performed with high accuracy without fail.
The operation member, the pressing-force adjustment portion and the paper gap switching portion may be formed by a gear mechanism and a link mechanism. Thus, since the operation member, the paper gap switching portion and the pressing-force adjustment portion can be formed by components having a relatively simple structure, the manufacturing cost can be reduced.
The operation member may include a first intermittent gear having an operation lever, a second intermittent gear arranged to be engageable with the first intermittent gear, and a third intermittent gear arranged to have the same rotation axis as the second intermittent gear; the pressing-force adjustment portion may include a fourth intermittent gear arranged to be engageable with the second intermittent gear and to have a shaft in which a part of a circumference is formed to be a flat surface, a fifth intermittent gear arranged to be engageable with the third intermittent gear, a following roller arm having one end onto which the following roller is rotatably mounted and another end rotatably attached to the shaft of the fourth intermittent gear, and a coil spring having an end fixed to the following roller, another end that is in contact with the shaft of the fourth intermittent gear and a center part fitted to approximately at a center of the following roller arm; and the paper gap switching portion may include a first link fitted to a shaft of the fifth intermittent gear at its one end, a second link hinged at its one end to another end of the first link, a third link hinged at its one end to another end of the second link, a fourth link hinged at its one end to the one end of the third link, a fifth link hinged at its one end to another end of the fourth link, and an eccentric cam, to which the recording head is attached, connected to another end of the third link, the fifth link being supported at its another end by a body of the ink jet recording apparatus.
Thus, since the operation member, the paper gap switching portion and the pressing-force adjustment portion can be formed by components having a relatively simple structure, the manufacturing cost can be reduced. Moreover, since the switching of the two series of driving operations can be mechanically realized by simple components, the switching operations can be performed with high accuracy without fail.
The ink jet recording apparatus may further include a click mechanism, formed integrally with the operation lever, operable to position the operation lever when the pressing force adjustment portion applies the pressure and when the pressing force adjustment portion release the pressure. Thus, as compared with a case where the click mechanism is formed separately from the operation lever, the touch of clock when the operation lever has been positioned is transmitted more directly, so that excellent touch of click can be obtained.
A position of the operation lever when the pressing-force adjustment portion applies the pressure may be arranged to be a part from a further position of the operation lever when the pressing-force adjustment portion releases the pressure. Thus, the user can clearly confirm whether the pressing-force adjustment portion is placed in a state of the pressure application or a state of the pressure release, only by viewing the operation lever. Therefore, error operations can be prevented.
The second link and the forth link may be arranged on the same side of the body of the recording apparatus. Thus, since the operation of the second link can be transmitted directly to the fourth link, it is possible to prevent the transmission failure caused by an unstable connection between the second and fourth links in a case where the second and fourth links are arranged on both side of the body, respectively.
The maximum one of the paper gaps is provided when the pressing-force adjustment portion release the pressure. Thus, since a distance between the print head and a recording state while the pressure is released and a distance between the feeding roller and the following roller are enough, it is possible to smoothly transport an even thick recording member between the respective components.
According to the second aspect of the present invention an ink jet recording apparatus having a feeding roller and a following roller operable to feed a recording medium while interposing the recording medium, and a recording head operable to eject ink droplets on the recording medium, the apparatus includes: a paper gap switching portion operable to switch a first paper gap and a second paper gap by moving the print head, the second paper gap being larger than the first paper gap; and a pressing-force adjustment portion operable to apply a pressure to the following roller or release the pressure to adjust a pressing force applied to the recording medium, wherein three states are switched by a single operation lever, the three states including a state where the first paper gap is set and the pressure is applied, another state where the second paper gap is set and the pressure is applied, and still another state where the pressure is released.
Thus, since the paper gap switching portion and the pressing-force adjustment portion can be operated by the operation of the operation member only, it is possible to smoothly perform the switching of the paper gaps and the adjustment of the pressing force without fail, improving the user""s operability. Moreover, since the functions of switching the paper gaps and adjusting the pressing force are integrated with the function of operating those functions, the structures of the operation member, the paper gap switching portion and the pressing-force adjustment portion can be made simple, so that the design can be simplified. Therefore, the design error can be reduced, and the cost for the manufacture and assembly and the number of the processes of the manufacture and assembly can be reduced.
Switching positions of the operation lever for switching the three states may be arranged in series. Thus, the operations of the operation lever can be performed in series, so that the printing setting can be performed more quickly.
Operations at the switching positions may be arranged in an order of setting the first paper gap and applying the pressure, setting the second paper gap and applying the pressure, and releasing the pressure. Thus, since the operations are arranged in an order of the printing for plain paper having a normal thickness, the printing for thick paper thicker than the plain paper, insertion/discharge of the paper, and various types of printing can be performed more quickly.
The paper gap switching portion and the pressing-force adjustment portion may be formed by a gear mechanism and a link mechanism. Thus, since the operation member, the paper gap switching portion and the pressing-force adjustment portion can be formed by components having a relatively simple structure, the manufacturing cost can be reduced.
The pressure applied by the pressing-force adjustment portion may be applied by an elastic member. Thus, the application and the release of the pressing force can be performed simply without fail.
According to the third aspect of the present invention, an ink jet recording apparatus, having a print head for ejecting ink droplets on a recording medium, for performing printing for the recording medium by making the print head elect the ink droplets on the recording medium while the print head moves in a main scanning direction and the recording medium is moved in a sub-scanning direction, the apparatus includes: a unidirectional printing portion operable to perform unidirectional printing in which the printing is performed in one of two directions contained in the main scanning direction; a bidirectional printing portion operable to perform bidirectional printing in which the printing is performed in both the two directions contained in the main scanning direction; and a printing-mode controlling portion operable to prohibit the bidirectional printing by the bidirectional printing portion when a thickness of the recording medium is out of a predetermined range, to force the unidirectional printing portion to perform the unidirectional printing. Thus, in a case of a recording medium having a thickness out of the predetermined range, such as thick paper or extra-thick paper, the unidirectional printing is forced to perform. Therefore, the printing quality can be prevented from degrading.
According to the fourth aspect of the present invention, an ink jet recording apparatus, having a print head operable to eject ink droplets on a recording medium, for performing printing by making the print head eject the ink droplets on the recording medium while the print head moves in a main scanning direction and the recording medium is moved in a sub-scanning direction, the apparatus includes: a main controlling unit including a unidirectional printing portion operable to perform unidirectional printing in which the printing is performed in one of two directions contained in the main scanning direction and a bidirectional printing portion operable to perform bidirectional printing in which the printing is performed in both the two directions of the main scanning direction; and a paper gap switching portion operable to switch a first paper gap and a second paper gap by moving the print head in accordance with a thickness of the recording medium, the second paper gap being larger than the first paper gap, wherein the main controlling unit further includes a printing-mode controlling portion operable to prohibit the bidirectional printing by the bidirectional printing portion and to force the unidirectional printing portion perform the unidirectional printing, when the second paper gap is set by the paper gap switching portion.
Thus, the bidirectional printing can be automatically prohibited only by setting the second paper gap by means of the paper gap switching portion. Therefore, the degradation of the printing quality can be prevented.
At least switching between the first paper gap and the second paper gap may be preformed by a single operation lever, and the printing-mode controlling portion may prohibit the bidirectional printing and forces the unidirectional printing portion to perform the unidirectional printing, when the second paper gap is set by the operation lever.
Thus, the bidirectional printing can be automatically prohibited only by setting the second paper gap by means of the single operation lever. Therefore, the degradation of the printing quality can be prevented.
Moreover, without the user""s selection, the unidirectional printing is automatically performed. Therefore, it is convenient to the user.
The main controlling unit may be arranged to allow selection of one of the unidirectional printing and the bidirectional printing, and even in a case where the bidirectional printing is selected, the printing-mode controlling portion may expand printing data generated for the bidirectional printing to obtain printing data for the unidirectional printing and only allows the unidirectional printing by the unidirectional printing portion to perform the unidirectional printing, when the thickness of the recording medium is out of a predetermined range and/or the second paper gap is set.
Thus, in a case of printing the thick paper or extra-thick paper while the user selected the bidirectional printing on the printer driver, for example, even when the main controlling unit received the printing data for the bidirectional printing from a host computer, the main controlling unit expands the received data again to be the data for the unidirectional printing and then performs the unidirectional printing. Therefore, without switching of the printing mode to the unidirectional printing by the user, the unidirectional printing is automatically performed, preventing the printing quality from being degraded without fail.
The paper gap-switching portion may be formed by a gear mechanism and a link mechanism.
The summary of the invention does not necessarily describe all necessary features of the present invention. The present invention may also be a sub-combination of the features described above. The above and other features and advantages of the present invention will become more apparent from the following description of the embodiments taken in conjunction with the accompanying drawings.